1. Field of the Invention
The present invention relates to lighting or signalling devices for motor vehicles. More specifically, the present invention relates to a motor vehicle lighting device allowing light beams of varied shapes to be formed while maintaining sufficient intensity to produce a signalling light such as, for example, the daytime lights known as DRLs (daytime running lights).
2. Description of the Related Art
A device of this type generally comprises:                at least one light source emitting light rays,        at least one light guiding sheet in which the light rays issuing from the light source spread by successive reflections.        
It is conventional to combine in a single housing a plurality of lighting or signalling functions so as to simplify the electrical wiring of these various functions in a motor vehicle. Each function comprises a light source, generally a reflector and optionally a lens, these various elements being arranged to provide a lighting or signalling beam, the geometric and photometric features of which have to comply with various regulations.
One solution for arranging a plurality of functions in a single housing is to use light guides so as thus to allow space to be saved.
Already known are light guides 18 shown in the example of FIG. 1. The light guides 18 are configured to extend in a circular pattern and they are disposed, for example, so as to surround the front perimeter of a passing beam headlamp. They generally comprise a face formed of a sequence of prisms or ridges and a cylindrical or toric output face. The prisms or ridges of the face send the light rays spreading into the guide toward the output face which provides therefrom an output beam which can, for example, fulfill the function of a parking light in a headlamp.
A solution of this type is particularly expensive since it requires a light source such as a halogen lamp, an elliptical reflector 10, a flexible fiber optic bundle 12 and a molded light guide 18, one of the faces of which is machined to form thereon prisms or ridges.
Moreover, this solution has the drawback that the light rays which spread into the guide are deflected in an uncontrolled manner by the ridges or the prisms, causing numerous losses in light intensity. The light beam produced has low intensity compared to the light source used at the start.
For specific functions requiring high intensity, it is necessary to have high-flux sources which are either expensive or tend to present heat problems, such as for example halogen-type lamps, rendering the design of the overall system expensive.
On the other hand, the periodic structure of the ridges or prisms is found in the emerging beam, so the light guide has a highly inhomogeneous appearance.
Therefore, the light guides forming a closed contour have inhomogeneities and often light points of greater intensity in the region of the bend 16 in the material of the light guide 18, and this further detracts from the quality of the lighting function and the visual quality of the device.
Finally, this solution has the drawback of a large overall size in order to be able to accommodate the light source, the reflector 10, the fiber optics 12 and the light guides 18.
Document EP-A-1,557,605 proposes a further lighting device which combines a plurality of reflectors, fiber optics and light guides and which requires a halogen lamp-type light source. Although this solution allows a specific number of functions to be included with a single lamp, it is expensive to carry out.
The prior documents do not propose effective solutions for obtaining a light beam with a particular shape and sufficient intensity to fulfill a lighting function such as the DRL function.